Over the course of the Covid-19 pandemic, Israel has been heralded as one of the best performing nations when it comes to vaccination against the disease.
Shortly after trials were complete on vaccines, the nation of 9.3 million raced to get as many jabs in arms as quickly as possible – after striking a deal with Pfizer to trade medical data in exchange for a steady supply of doses.
Once the majority of the Middle Eastern nation's adult population was fully vaccinated a few months ago, Israel lifted virtually all Covid-19 restrictions and a sense of normality returned.
However, anybody who has been following the impact of the Delta strain on Israel knows it has not been plain sailing ever since.
When daily case numbers hovered around zero at the beginning of their summer, Israel's businesses reopened, mass gatherings resumed, and face masks were tossed away as people flocked to beaches and restaurants.
The optimism didn't last long. By the beginning of September, cases had climbed to more than 20,000 a day, hospitalisations were rising and more than 50 deaths a day were being recorded.
Things were starting to look better at the beginning of this month – with cases and deaths dropping – but as winter begins to rear its head in the Northern Hemisphere, there is a fierce debate happening about what the next steps are for Israel.
It is all coming to a head this week, as the goalposts for vaccinated residents are about to shift in a major way.
From yesterday, the conditions for the nation's Covid Green Pass – essentially a vaccine passport that allows inoculated residents to enter indoor venues – have been radically altered.
The shake-up means Israel is now the first country in the world to no longer provide its vaccination certificate to citizens who had received their second vaccine dose more than six months ago.
Under the new guidelines, people must have received a third jab, a booster shot, to be eligible for a green pass.
People who have received two vaccine doses, and those who have recovered from coronavirus, will be issued passes valid for six months after the date of their third booster shot or recovery.
It means that nearly 2 million people will lose their vaccination passport in the coming days – with the cull beginning yesterday.
It's a big blow for residents who don't meet the criteria because the loss of their Green Pass certificates will prevent them from entering public spaces, including restaurants, hotels, clubs, cultural venues and large private gatherings.
However, people will only have those privileges stripped away from them if they are eligible for a third shot and have not taken it up.
In response to its summer outbreak, Israel launched an aggressive booster campaign to shore up waning vaccine efficacy in its population.
Over 60 per cent of Israel's population has received two doses of the Pfizer vaccine and nearly 3.5 million of Israel's 9.3 million citizens have received a booster dose of the vaccine.
However, at least 2 million more have received just two doses, and many will lose the privileges bestowed by the green pass which comes into effect this week.
The new system means unvaccinated people can only gain entry with a proof of a negative rapid test carried out at an authorised test station, which is valid for 24 hours, or a negative PCR test valid for 72 hours.
There has been a wave of opposition to the new system, with hundreds of Israelis staging demonstrations around the country in protest of it.
Footage of the demonstrations on Sunday shows convoys of cars clogging morning commutes as many Israelis who returned to work after September's Jewish High Holidays. Opponents of the system said it is a form of forced vaccination.
The change in policy came after Israeli health officials and experts warned of a significant waning of immunity in people five or six months after their second Pfizer dose.
Overseas studies have also shown the need for booster Pfizer doses after several months.
A large and recent study by the University of Oxford found the efficacy of the Pfizer jab fell by 22 per cent per month – from an original 84 per cent for adults overall.
According to data published by the American Centers for Disease Control and Prevention last month, the protection afforded by the Pfizer vaccine begins to decline around four months after the vaccination date.
The US, UK and other countries including Israel have already approved booster doses for older people who had the Pfizer vaccine six to eight months after their first doses.
Australia's government advisory body on vaccines is expected to rule on whether Australians need a booster dose in coming weeks.
Israel, meanwhile, is pushing ahead with its revised green pass plan.
"Now is the time to be strict about the Green Pass, be cautious and not become complacent," Israel Prime Minister Naftali Bennett said late on Saturday. An early advocate of the third dose, Bennett said it saved lives and allowed the economy to remain open.
Professor Nadav Davidovitch, head of the Israeli Association of Public Health Physicians said requiring Israelis to receive the booster in order to be considered fully vaccinated and eligible for the Green Pass was "the right decision".
He told local media the Green Pass is "not a prize or punishment" but rather a public health measure based on consideration of clinical and epidemiological data.
Israel changed its policy regarding vaccination status earlier than other countries because it began vaccinating earlier (last December), and enough time has passed "to see a sharp rise in community transmission", he said.
He added that the data indicated that the increase in protection following a third shot could "be 10 times and up, compared to people who got the second dose".